This paper describes the strengthening of two concrete natural draught cooling towers at Ironbridge Power Station. Details are given of site investigation, mini-pile foundation strengthening, column jacking and the use of pigmented fly ash concrete for cast-in-situ mantles. The design of the foundation strengthening and in-situ mantle are described. The construction of external mantles around the existing shells made use of a climbing rig access system and included the pumping of concrete to heights of 110 m.